(Not Applicable)
(Not Applicable)
The present invention relates generally to conveying apparatus, and more particularly to a pneumatic conveying apparatus that rapidly conveys products while safely reducing the terminal velocity of the product to avoid damaging the same.
Mechanical conveyors have been commonly used for transporting articles. However, such prior art mechanical conveyers are costly, possess substantial product contamination concerns and often time damage fragile product such as cereals and/or coffee beans.
To address the problems of mechanical conveyors, pneumatic conveyors have heretofor been developed. In conventional pneumatic conveyors, product is conveyed in a pipe or conduit via air, i.e., vacuum. Articles to be conveyed in such pneumatic systems require a sufficient initial velocity to prevent product dropout during conveyance; yet, the terminal velocity of the articles must be reduced to prevent product damage and degradation.
The prior art mechanisms for reducing the terminal velocity of the articles under pneumatic conveyance typically comprise using a cyclone or alternatively gradually increasing conduit/line size through the conveyance path. In a cyclone, mechanical frictional deceleration often causes the article to break and become damaged. By gradually increasing the line size, the articles often time drop out causing the conveyor line to plug.
As such, there exists a substantial need in the art for an improved pneumatic conveyor system that safely conveys fragile product without damage and eliminate product drop out during transport.
To obtain a fluent conveyance of articles without breakage or damage, the present invention provides a pneumatic conveying apparatus having a unique terminal velocity dissipater. Instead of using the prior art mechanical decelerating methods such as a cyclone or gradually increasing the line size for the articles under conveyance, the present invention utilizes a pressure gradient (dead) air cushion formed at the terminal end of the conveyor. Traveling through the air cushion, the velocity of the articles is rapidly reduced without substantially physical impact or friction thereby significantly reducing damage or breakage of the articles being conveyed.
In the preferred embodiment of the invention, the pneumatic conveying apparatus comprises two valves installed along the conveyor line path for the articles to be conveyed. Both valves are initially opened to a pressure source to allow a high initial force to be applied to the product to initiate flow and ensure against product dropout thereby establishing a steady product flow from the entrance to the exit of the conveyor line path.
Subsequently, a second one of the valves is closed, or supplied with a reduced pressure or a pressure in an inverse direction, to the initial pressure to establish a dead air space at a terminal end of the conveyor line path while maintaining sufficient inertia and velocity to continue product flow toward the terminal end of the conveyor line path. The articles flowing from the open valve to the terminal end of the conveyor line path experience a draw back pressure gradient due to the vacuum supplied by the open valve; that is, a (dead) air cushion formed between the open valve and the exit of the line path to cause a controlled and dampened deceleration of the articles at the terminal end of the line path.
In the above embodiment, as the articles are not decelerated by any frictional force or physical contact, damage or breakage of the articles is prevented with articles conveyed with velocities of about 8000 ft/min to about 9000 ft/min in a conveyor line path having a length of about 200 ft to about 300 ft.
In another embodiment of the present invention, only one valve is installed on the conveyor line path. By supplying a pressure to the conveyor line path via the valve, the product is drawn into the conveyor line path and accelerated to a required velocity. After a steady state flow of the product is established, the pressure is adjusted to a magnitude to form a gradient pressure at a terminal end of the conveyor line path. The terminal velocity of the product is thus retarded by the gradient pressure while a sufficient internia and velocity is maintained to continue product flow towards the terminal end.
A container is further provided to connect with the exit of the conveyor line path. The container is so designed that the article entering therein is directed tangentially about an inside diameter thereof. Preferably, the flow velocity of the articles is monitored to determine the timing for closing the second one of the valves adjacent the terminal end of the conveyor line path, to ensure that the product flows within the conveyor at sufficient velocity to prevent product dropout yet avoid product damage heretofore occurring at the terminal end of the conduit line.